1. Field of the Invention
The present invention relates to an apparatus and a method for controlling an optical disc write power used for an optical disc writer.
2. Description of the Related Art
Many optical disc writers have a configuration in which, in addition to the base power, an overdrive power is added to the beginning portion of the base power to prevent a write mark from being formed into a teardrop shape. In general, this type of optical disc writer has a read power APC (Auto Power Control) circuit that samples and holds (S/H) the read power level to keep the read power at a desired value and a base power APC circuit that samples and holds the base power level to keep the base power at a desired value. For the overdrive power, the writer has a configuration in which an overdrive current value corresponding to a predetermined power, or a current that is split from the base power current, is added as the overdrive current value.
However, because the overdrive pulse width is narrower than the base pulse width, it is difficult to stably sample and hold the overdrive power level and to perform APC processing that keeps the overdrive power at a desired value. On the other hand, as the write speed of an optical disc is increased and its write quality is improved recently, it is required that this overdrive amount be precisely output even if there is a variation in the circuit characteristics, the laser diode (LD) ages, or the drive temperature changes.